Can I restart or is it better to finish a playthrough first?

I'd say I'm about 3/5th through and I'm really starting to notice ways I screwed up on the way here. I'm strongly tempted to just restart now that I have a better understanding of the game, but I wondered if there were any reasons to finish the playthrough before restarting. I don't know if there's a ng+ or weird meta stuff that I would be kicking myself for not completing beforehand.